The effects of multi-age grouping on achievement and self-concept were studied. The achievement variables examined were reading and mathematics achievement as measured by the Stanford Achievement Tests. The Piers-Harris Children's Self-Concept Scale was used to measure self-concept. The groups studied consisted of single-age and multi-age classrooms of children in grades one through five. No significant differences were found between children in multi-age and single-age classrooms on any of the achievement measures. The multi-age classrooms had significantly higher mean scores on one of the six factors in the self-concept scale--happiness and satisfaction. The multi-age classrooms had slightly but consistently higher mean scores on the other five factor scores and on the total self-concept score but the differences were not significant. (Author)